diff --git a/src/lib/__tests__/recurrence-overrides.test.ts b/src/lib/__tests__/recurrence-overrides.test.ts
new file mode 100644
index 00000000..1fcc0e80
--- /dev/null
+++ b/src/lib/__tests__/recurrence-overrides.test.ts
@@ -0,0 +1,143 @@
+import { describe, it, expect } from 'vitest';
+import type { CalendarEvent } from '../../api/types';
+import {
+  buildAllScopeUpdates,
+  buildFutureSeriesData,
+  buildRecurrenceOverridePatch,
+  isRecurringSeriesMember,
+  truncateRecurrenceRules,
+} from '../recurrence-overrides';
+
+const master: CalendarEvent = {
+  id: 'ev-1',
+  uid: 'uid-1',
+  calendarIds: { 'cal-1': true },
+  title: 'Standup',
+  start: '2026-03-02T09:00:00',
+  duration: 'PT30M',
+  timeZone: 'Europe/Berlin',
+  recurrenceRules: [{ frequency: 'daily', interval: 1, count: 10 }],
+};
+
+const occurrence: CalendarEvent = {
+  ...master,
+  id: 'ev-1:2026-03-04T08:00:00.000Z',
+  originalId: 'ev-1',
+  start: '2026-03-04T09:00:00',
+  recurrenceId: '2026-03-04T08:00:00.000Z',
+};
+
+describe('buildRecurrenceOverridePatch', () => {
+  it('writes the whole override under one recurrenceOverrides pointer', () => {
+    const patch = buildRecurrenceOverridePatch(
+      { title: 'Moved', start: '2026-03-04T10:00:00', calendarIds: { x: true }, uid: 'nope' },
+      '2026-03-04T08:00:00.000Z',
+    );
+    expect(patch).toEqual({
+      'recurrenceOverrides/2026-03-04T08:00:00.000Z': {
+        title: 'Moved',
+        start: '2026-03-04T10:00:00',
+      },
+    });
+  });
+
+  it('never leaks series-level keys or recurrenceId into the override', () => {
+    const patch = buildRecurrenceOverridePatch(
+      {
+        recurrenceRules: [{ frequency: 'weekly' }],
+        recurrenceOverrides: {},
+        excludedRecurrenceRules: [],
+        recurrenceId: '2026-03-04',
+        id: 'x',
+        '@type': 'Event',
+        description: 'kept',
+      },
+      '2026-03-04',
+    );
+    expect(patch['recurrenceOverrides/2026-03-04']).toEqual({ description: 'kept' });
+  });
+});
+
+describe('isRecurringSeriesMember', () => {
+  it('detects masters and expanded occurrences but not plain shared events', () => {
+    expect(isRecurringSeriesMember(master)).toBe(true);
+    expect(isRecurringSeriesMember(occurrence)).toBe(true);
+    expect(isRecurringSeriesMember({ recurrenceRules: [] })).toBe(false);
+    expect(isRecurringSeriesMember({ originalId: 'raw' } as CalendarEvent)).toBe(false);
+  });
+});
+
+describe('truncateRecurrenceRules', () => {
+  it('ends the rule one second before the occurrence slot and drops count', () => {
+    const rules = truncateRecurrenceRules(master.recurrenceRules, occurrence);
+    expect(rules).toHaveLength(1);
+    expect(rules[0].count).toBeUndefined();
+    // recurrenceId is the UTC instant; until is local wall-clock, one second earlier.
+    const expected = new Date('2026-03-04T08:00:00.000Z');
+    expected.setSeconds(expected.getSeconds() - 1);
+    const pad = (n: number) => String(n).padStart(2, '0');
+    const local =
+      `${expected.getFullYear()}-${pad(expected.getMonth() + 1)}-${pad(expected.getDate())}` +
+      `T${pad(expected.getHours())}:${pad(expected.getMinutes())}:${pad(expected.getSeconds())}`;
+    expect(rules[0].until).toBe(local);
+    expect(rules[0].frequency).toBe('daily');
+  });
+
+  it('treats an all-day recurrenceId as a local date', () => {
+    const rules = truncateRecurrenceRules(
+      [{ frequency: 'weekly' }],
+      { recurrenceId: '2026-03-04', start: '2026-03-04T00:00:00' },
+    );
+    expect(rules[0].until).toBe('2026-03-03T23:59:59');
+  });
+});
+
+describe('buildAllScopeUpdates', () => {
+  it('drops an unchanged occurrence start so the master is not moved', () => {
+    const out = buildAllScopeUpdates(
+      { title: 'Renamed', start: '2026-03-04T09:00:00', recurrenceId: 'x' },
+      occurrence,
+      master,
+    );
+    expect(out).toEqual({ title: 'Renamed' });
+  });
+
+  it('applies the delta of a moved occurrence to the master start', () => {
+    const out = buildAllScopeUpdates(
+      { start: '2026-03-04T10:30:00' },
+      occurrence,
+      master,
+    );
+    expect(out.start).toBe('2026-03-02T10:30:00');
+  });
+
+  it('keeps start when editing the master itself', () => {
+    const out = buildAllScopeUpdates({ start: '2026-03-05T09:00:00' }, master, master);
+    expect(out.start).toBe('2026-03-05T09:00:00');
+  });
+});
+
+describe('buildFutureSeriesData', () => {
+  it('clones the master with the original rules, edits on top and the occurrence start', () => {
+    const data = buildFutureSeriesData(
+      master,
+      master.recurrenceRules ?? null,
+      occurrence,
+      { title: 'New title' },
+    );
+    expect(data.title).toBe('New title');
+    expect(data.start).toBe('2026-03-04T09:00:00');
+    expect(data.recurrenceRules).toEqual(master.recurrenceRules);
+    expect(data.duration).toBe('PT30M');
+    expect(data.timeZone).toBe('Europe/Berlin');
+    expect('id' in data).toBe(false);
+    expect('uid' in data).toBe(false);
+    expect('recurrenceId' in data).toBe(false);
+  });
+
+  it('prefers a start the user moved', () => {
+    const data = buildFutureSeriesData(master, null, occurrence, { start: '2026-03-04T11:00:00' });
+    expect(data.start).toBe('2026-03-04T11:00:00');
+    expect('recurrenceRules' in data).toBe(false);
+  });
+});
diff --git a/src/lib/recurrence-overrides.ts b/src/lib/recurrence-overrides.ts
new file mode 100644
index 00000000..92943327
--- /dev/null
+++ b/src/lib/recurrence-overrides.ts
@@ -0,0 +1,161 @@
+import { format, parseISO } from 'date-fns';
+import type { CalendarEvent, RecurrenceRule } from '../api/types';
+
+/** Identity / whole-series keys that must never go into a single-occurrence override. */
+export const RECURRENCE_OVERRIDE_IMMUTABLE_KEYS = [
+  'id',
+  'uid',
+  '@type',
+  'calendarIds',
+  'recurrenceRules',
+  'recurrenceOverrides',
+  'excludedRecurrenceRules',
+] as const;
+
+/**
+ * Build the "This event only" override patch for a recurring master.
+ *
+ * Why one pointer: a JMAP nested pointer can't create a missing intermediate,
+ * so the override object has to be set whole at `recurrenceOverrides/<id>`, not
+ * field-by-field (#774). Mirrors webmail's lib/recurrence-overrides.ts.
+ */
+export function buildRecurrenceOverridePatch(
+  updates: Partial<CalendarEvent>,
+  recurrenceId: string,
+): Record<string, unknown> {
+  const immutable = new Set<string>(RECURRENCE_OVERRIDE_IMMUTABLE_KEYS);
+  const override: Record<string, unknown> = {};
+  for (const [key, value] of Object.entries(updates)) {
+    if (immutable.has(key)) continue;
+    if (key === 'recurrenceId') continue;
+    override[key] = value;
+  }
+  return { [`recurrenceOverrides/${recurrenceId}`]: override };
+}
+
+/**
+ * A recurring series member is a master (has recurrenceRules) or an expanded
+ * occurrence (has recurrenceId) — those get the this/future/all scope dialog.
+ * Note: `originalId` alone is not a signal, shared/group events carry it for
+ * id-namespacing even when they aren't recurring.
+ */
+export function isRecurringSeriesMember(
+  event: Pick<CalendarEvent, 'recurrenceRules' | 'recurrenceId'>,
+): boolean {
+  return !!event.recurrenceRules?.length || !!event.recurrenceId;
+}
+
+/** The original slot of an occurrence as a local wall-clock Date. */
+export function occurrenceSlotDate(
+  event: Pick<CalendarEvent, 'recurrenceId' | 'start'>,
+): Date {
+  // recurrenceId is either "yyyy-MM-dd" (all-day) or the occurrence instant
+  // as UTC ISO; parseISO treats a date-only value as local midnight, which is
+  // what the RRULE `until` below needs. `new Date("yyyy-MM-dd")` would read
+  // it as UTC and shift the day in any non-UTC zone.
+  return parseISO(event.recurrenceId || event.start);
+}
+
+/**
+ * "This and following": end the master's rules one second before the chosen
+ * occurrence. `count` is dropped so the truncated rule is bounded by `until`
+ * alone (a rule can't carry both). Mirrors webmail's truncateRecurrenceAtEvent.
+ */
+export function truncateRecurrenceRules(
+  rules: RecurrenceRule[] | undefined | null,
+  occurrence: Pick<CalendarEvent, 'recurrenceId' | 'start'>,
+): RecurrenceRule[] {
+  const untilDate = occurrenceSlotDate(occurrence);
+  untilDate.setSeconds(untilDate.getSeconds() - 1);
+  const until = format(untilDate, "yyyy-MM-dd'T'HH:mm:ss");
+  return (rules || []).map((rule) => {
+    const { count: _count, ...rest } = rule;
+    return { ...rest, until };
+  });
+}
+
+/**
+ * Updates for the "All events" scope. The editor seeds its date fields from
+ * the tapped occurrence, so an unchanged `start` must not be written to the
+ * master (that would move the whole series onto the occurrence's date and
+ * make the earlier occurrences vanish). When the user did move the occurrence,
+ * the same delta is applied to the master's start instead.
+ */
+export function buildAllScopeUpdates(
+  updates: Partial<CalendarEvent>,
+  occurrence: Pick<CalendarEvent, 'start' | 'recurrenceId'>,
+  master: Pick<CalendarEvent, 'start'>,
+): Partial<CalendarEvent> {
+  const out: Partial<CalendarEvent> = { ...updates };
+  delete (out as Record<string, unknown>).recurrenceId;
+  if (!out.start) return out;
+  if (!occurrence.recurrenceId) return out; // editing the master itself
+  const nextStart = parseISO(out.start);
+  const occurrenceStart = parseISO(occurrence.start);
+  const masterStart = parseISO(master.start);
+  if (
+    isNaN(nextStart.getTime()) ||
+    isNaN(occurrenceStart.getTime()) ||
+    isNaN(masterStart.getTime())
+  ) {
+    delete out.start;
+    return out;
+  }
+  const delta = nextStart.getTime() - occurrenceStart.getTime();
+  if (delta === 0) {
+    delete out.start;
+    return out;
+  }
+  const shifted = new Date(masterStart.getTime() + delta);
+  out.start = format(shifted, "yyyy-MM-dd'T'HH:mm:ss");
+  return out;
+}
+
+/**
+ * The new series created for "This and following": the master's series-level
+ * fields, the original (untruncated) rules, the user's edits on top, and the
+ * occurrence's slot as the start unless the user moved it.
+ */
+export function buildFutureSeriesData(
+  master: CalendarEvent,
+  originalRules: RecurrenceRule[] | null,
+  occurrence: Pick<CalendarEvent, 'start' | 'recurrenceId'>,
+  updates: Partial<CalendarEvent>,
+): Partial<CalendarEvent> {
+  const occurrenceStart = occurrence.start;
+  const data: Partial<CalendarEvent> = {
+    title: master.title,
+    description: master.description,
+    duration: master.duration,
+    timeZone: master.timeZone,
+    calendarIds: { ...master.calendarIds },
+    status: master.status,
+    freeBusyStatus: master.freeBusyStatus,
+    showWithoutTime: master.showWithoutTime,
+    participants: master.participants,
+    organizerCalendarAddress: master.organizerCalendarAddress,
+    alerts: master.alerts,
+    useDefaultAlerts: master.useDefaultAlerts,
+    locations: master.locations,
+    virtualLocations: master.virtualLocations,
+    recurrenceRules: originalRules ?? undefined,
+    ...updates,
+    start: updates.start || occurrenceStart,
+  };
+  const raw = data as Record<string, unknown>;
+  delete raw.id;
+  delete raw.uid;
+  delete raw.recurrenceId;
+  delete raw.recurrenceOverrides;
+  delete raw.excludedRecurrenceRules;
+  delete raw.utcStart;
+  delete raw.utcEnd;
+  delete raw.originalId;
+  delete raw.originalCalendarIds;
+  delete raw.accountId;
+  delete raw.isShared;
+  for (const key of Object.keys(raw)) {
+    if (raw[key] === undefined) delete raw[key];
+  }
+  return data;
+}
diff --git a/src/screens/CalendarScreen.tsx b/src/screens/CalendarScreen.tsx
index 8207bf8e..a98bae7d 100644
--- a/src/screens/CalendarScreen.tsx
+++ b/src/screens/CalendarScreen.tsx
@@ -1,5 +1,6 @@
 import React from 'react';
 import {
+  Alert,
   View,
   Text,
   StyleSheet,
@@ -55,19 +56,28 @@ import {
   applySharedCalendarColors,
   buildEventDayIndex,
   eventsOnDayFromIndex,
+  getPrimaryCalendarId,
   pickUnusedCalendarColor,
   sharedCalendarColorKey,
   type EventDayIndex,
   type TimeFormat,
 } from '../lib/calendar-utils';
 import { buildReplyTo } from '../lib/calendar-invitation';
+import {
+  buildAllScopeUpdates,
+  buildFutureSeriesData,
+  buildRecurrenceOverridePatch,
+  isRecurringSeriesMember,
+  truncateRecurrenceRules,
+} from '../lib/recurrence-overrides';
 import { generateBirthdayEvents, createBirthdayCalendar, BIRTHDAY_CALENDAR_ID } from '../lib/birthday-calendar';
 import { useContactsStore } from '../stores/contacts-store';
-import type { Calendar, CalendarEvent } from '../api/types';
+import { useLocaleStore } from '../stores/locale-store';
+import type { Calendar, CalendarEvent, RecurrenceRule } from '../api/types';
 
 type ViewMode = 'month' | 'week' | 'agenda';
 type PendingAction =
-  | { kind: 'edit'; event: CalendarEvent }
+  | { kind: 'edit'; event: CalendarEvent; updates: Partial<CalendarEvent>; calendarId: string }
   | { kind: 'delete'; event: CalendarEvent }
   | null;
 
@@ -115,6 +125,7 @@ function headerTitle(
 export default function CalendarScreen() {
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
+  const t = useLocaleStore((s) => s.t);
   const calendarDefaultView = useSettingsStore((s) => s.calendarDefaultView);
   const calendarFirstDayOfWeek = useSettingsStore((s) => s.calendarFirstDayOfWeek);
   const calendarShowWeekNumbers = useSettingsStore((s) => s.calendarShowWeekNumbers);
@@ -154,6 +165,7 @@ export default function CalendarScreen() {
   const createEvent = useCalendarStore((s) => s.createEvent);
   const updateEvent = useCalendarStore((s) => s.updateEvent);
   const deleteEvent = useCalendarStore((s) => s.deleteEvent);
+  const getMasterEvent = useCalendarStore((s) => s.getMasterEvent);
   const rsvpEvent = useCalendarStore((s) => s.rsvpEvent);
   const importEvents = useCalendarStore((s) => s.importEvents);
   const tasks = useCalendarStore((s) => s.tasks);
@@ -315,24 +327,13 @@ export default function CalendarScreen() {
     [],
   );
 
-  // A recurring series member is a master (has recurrenceRules) or an expanded
-  // occurrence (has recurrenceId) — those get the this/all scope dialog. Note:
-  // we must NOT key off originalId here, since shared/group events now carry it
-  // for id-namespacing even when they aren't recurring.
-  const isRecurringSeriesMember = React.useCallback(
-    (event: CalendarEvent) => !!event.recurrenceRules?.length || !!event.recurrenceId,
-    [],
-  );
-
+  // Editing a series member opens the editor directly; the this/future/all
+  // scope question is asked on save (like webmail), once we know the edits.
   const handleEditFromDetail = React.useCallback((event: CalendarEvent) => {
     if (isReadOnlyEvent(event)) { setDetailEvent(null); return; }
     setDetailEvent(null);
-    if (isRecurringSeriesMember(event)) {
-      setPendingAction({ kind: 'edit', event });
-    } else {
-      openEditDirect(event);
-    }
-  }, [openEditDirect, isReadOnlyEvent, isRecurringSeriesMember]);
+    openEditDirect(event);
+  }, [openEditDirect, isReadOnlyEvent]);
 
   const handleDeleteFromDetail = React.useCallback((event: CalendarEvent) => {
     if (isReadOnlyEvent(event)) { setDetailEvent(null); return; }
@@ -342,30 +343,130 @@ export default function CalendarScreen() {
     } else {
       void deleteEvent(event.id);
     }
-  }, [deleteEvent, isReadOnlyEvent, isRecurringSeriesMember]);
+  }, [deleteEvent, isReadOnlyEvent]);
+
+  // "This and following": end the master at the occurrence and hand back the
+  // master plus its untouched rules so the caller can start a new series (or
+  // roll back). Port of webmail's truncateRecurrenceAtEvent.
+  const truncateRecurrenceAtEvent = React.useCallback(
+    async (event: CalendarEvent) => {
+      const master = await getMasterEvent(event);
+      if (!master) return null;
+      const originalRules = master.recurrenceRules
+        ? (JSON.parse(JSON.stringify(master.recurrenceRules)) as RecurrenceRule[])
+        : null;
+      await updateEvent(master.id, {
+        recurrenceRules: truncateRecurrenceRules(master.recurrenceRules, event),
+      });
+      return { master, originalRules };
+    },
+    [getMasterEvent, updateEvent],
+  );
 
   const handleScopeSelect = React.useCallback(
     async (scope: RecurrenceEditScope) => {
       const action = pendingAction;
       setPendingAction(null);
       if (!action) return;
-      // For the first pass, treat all scopes as "all" - proper override
-      // handling lives in the store's update/delete path against originalId.
-      // TODO: implement "this only" via recurrenceOverrides write, and
-      // "this and following" via excludedRecurrenceRules + new master.
-      if (action.kind === 'edit') {
-        openEditDirect(action.event);
-      } else {
-        await deleteEvent(action.event.id);
+      const { event } = action;
+      try {
+        if (action.kind === 'edit') {
+          const { updates } = action;
+          switch (scope) {
+            case 'this': {
+              if (event.recurrenceId) {
+                // Client-side expanded occurrence: write a one-shot override
+                // on the master instead of touching the series.
+                await updateEvent(event.id, buildRecurrenceOverridePatch(updates, event.recurrenceId));
+              } else {
+                await updateEvent(event.id, updates);
+              }
+              break;
+            }
+            case 'this_and_future': {
+              const result = await truncateRecurrenceAtEvent(event);
+              if (!result) throw new Error('Master event not found');
+              const { master, originalRules } = result;
+              const newEventData = buildFutureSeriesData(master, originalRules, event, updates);
+              delete newEventData.calendarIds;
+              const targetCalendarId =
+                action.calendarId || getPrimaryCalendarId(master) || '';
+              try {
+                await createEvent(newEventData, targetCalendarId);
+              } catch (createError) {
+                // Roll back the truncation so the series isn't left cut short.
+                try {
+                  await updateEvent(master.id, { recurrenceRules: originalRules ?? [] });
+                } catch {
+                  // The rollback failing is reported through the original error.
+                }
+                throw createError;
+              }
+              break;
+            }
+            case 'all': {
+              const master = await getMasterEvent(event);
+              if (!master) throw new Error('Master event not found');
+              await updateEvent(master.id, buildAllScopeUpdates(updates, event, master));
+              break;
+            }
+          }
+        } else {
+          switch (scope) {
+            case 'this': {
+              if (event.recurrenceId) {
+                await updateEvent(event.id, {
+                  [`recurrenceOverrides/${event.recurrenceId}`]: { excluded: true },
+                });
+              } else {
+                await deleteEvent(event.id);
+              }
+              break;
+            }
+            case 'this_and_future': {
+              const result = await truncateRecurrenceAtEvent(event);
+              if (!result) throw new Error('Master event not found');
+              break;
+            }
+            case 'all': {
+              const master = await getMasterEvent(event);
+              if (!master) throw new Error('Master event not found');
+              await deleteEvent(master.id);
+              break;
+            }
+          }
+        }
+      } catch (err) {
+        Alert.alert(
+          t('calendar.notifications.event_error', 'Something went wrong'),
+          err instanceof Error ? err.message : undefined,
+        );
+      }
+      try {
+        await refresh();
+      } catch {
+        // Best effort — the next navigation refetches anyway.
       }
     },
-    [pendingAction, openEditDirect, deleteEvent],
+    [pendingAction, updateEvent, deleteEvent, createEvent, getMasterEvent, truncateRecurrenceAtEvent, refresh, t],
   );
 
   const handleSave = React.useCallback(
     async (data: Partial<CalendarEvent>, calendarId: string) => {
       if (modalEvent) {
-        await updateEvent(modalEvent.id, data);
+        const updates: Partial<CalendarEvent> = { ...data };
+        // Moving the event to another calendar: the store remaps the store id
+        // onto the owning account's raw calendar id.
+        if (calendarId && calendarId !== getPrimaryCalendarId(modalEvent)) {
+          updates.calendarIds = { [calendarId]: true };
+        }
+        if (isRecurringSeriesMember(modalEvent)) {
+          // Ask which occurrences the edit applies to; the actual write
+          // happens in handleScopeSelect.
+          setPendingAction({ kind: 'edit', event: modalEvent, updates, calendarId });
+          return;
+        }
+        await updateEvent(modalEvent.id, updates);
       } else {
         await createEvent(data, calendarId);
       }
@@ -376,6 +477,10 @@ export default function CalendarScreen() {
   const handleDeleteFromModal = React.useCallback(
     async (event: CalendarEvent) => {
       setModalVisible(false);
+      if (isRecurringSeriesMember(event)) {
+        setPendingAction({ kind: 'delete', event });
+        return;
+      }
       await deleteEvent(event.id);
     },
     [deleteEvent],
diff --git a/src/stores/__tests__/calendar-store.test.ts b/src/stores/__tests__/calendar-store.test.ts
index 3f6f4f9d..bec13c4c 100644
--- a/src/stores/__tests__/calendar-store.test.ts
+++ b/src/stores/__tests__/calendar-store.test.ts
@@ -417,5 +417,85 @@ describe('calendar-store', () => {
       expect(useCalendarStore.getState().events).toHaveLength(1);
       expect(useCalendarStore.getState().events[0].id).toBe('ev2');
     });
+
+    it('should drop every expanded occurrence of a destroyed master and refetch', async () => {
+      useCalendarStore.setState({
+        calendars: [{ id: 'cal-1', name: 'Personal' } as any],
+        loadedRange: { after: '2026-03-01T00:00:00Z', before: '2026-03-31T00:00:00Z' },
+        events: [
+          { id: 'ev1:a', originalId: 'ev1', recurrenceId: 'a', recurrenceRules: [{ frequency: 'daily' }] } as any,
+          { id: 'ev1:b', originalId: 'ev1', recurrenceId: 'b', recurrenceRules: [{ frequency: 'daily' }] } as any,
+          { id: 'ev2' } as any,
+        ],
+      });
+      mockDeleteEvents.mockResolvedValue(undefined);
+      mockQueryEvents.mockResolvedValue([]);
+
+      await useCalendarStore.getState().deleteEvent('ev1:a');
+
+      expect(mockDeleteEvents).toHaveBeenCalledWith(['ev1'], undefined, undefined);
+      // The visible range was reloaded (empty here).
+      expect(mockQueryEvents).toHaveBeenCalled();
+    });
+  });
+
+  describe('recurring series mutations', () => {
+    it('updateEvent on an occurrence patches the master and refetches the range', async () => {
+      useCalendarStore.setState({
+        calendars: [{ id: 'cal-1', name: 'Personal' } as any],
+        loadedRange: { after: '2026-03-01T00:00:00Z', before: '2026-03-31T00:00:00Z' },
+        events: [
+          { id: 'ev1:a', originalId: 'ev1', recurrenceId: 'a', title: 'Old', recurrenceRules: [{ frequency: 'daily' }] } as any,
+          { id: 'ev1:b', originalId: 'ev1', recurrenceId: 'b', title: 'Old', recurrenceRules: [{ frequency: 'daily' }] } as any,
+        ],
+      });
+      mockUpdateEvent.mockResolvedValue(undefined);
+      mockQueryEvents.mockResolvedValue(['ev1']);
+      mockGetEvents.mockResolvedValue([
+        { id: 'ev1', title: 'New', start: '2026-03-02T09:00:00', recurrenceRules: [{ frequency: 'daily', count: 2 }], calendarIds: { 'cal-1': true } },
+      ]);
+
+      await useCalendarStore.getState().updateEvent('ev1:a', { 'recurrenceOverrides/a': { title: 'New' } });
+
+      expect(mockUpdateEvent).toHaveBeenCalledWith('ev1', { 'recurrenceOverrides/a': { title: 'New' } }, undefined, undefined);
+      // Refetched: siblings now carry the server's state.
+      const events = useCalendarStore.getState().events;
+      expect(events.length).toBeGreaterThan(0);
+      expect(events.every((e) => e.title === 'New')).toBe(true);
+    });
+
+    it('updateEvent remaps namespaced calendarIds to the raw server id', async () => {
+      useCalendarStore.setState({
+        calendars: [
+          { id: 'cal-1', name: 'Personal' } as any,
+          { id: 'acc-2:cal-9', originalId: 'cal-9', accountId: 'acc-2', name: 'Shared', isShared: true } as any,
+        ],
+        events: [{ id: 'ev1', calendarIds: { 'cal-1': true } } as any],
+      });
+      mockUpdateEvent.mockResolvedValue(undefined);
+
+      await useCalendarStore.getState().updateEvent('ev1', { calendarIds: { 'acc-2:cal-9': true } });
+
+      expect(mockUpdateEvent).toHaveBeenCalledWith('ev1', { calendarIds: { 'cal-9': true } }, undefined, undefined);
+    });
+
+    it('getMasterEvent fetches the master an occurrence points at', async () => {
+      useCalendarStore.setState({ calendars: [], events: [] });
+      mockGetEvents.mockResolvedValue([{ id: 'ev1', start: '2026-03-02T09:00:00', recurrenceRules: [{ frequency: 'daily' }] }]);
+
+      const master = await useCalendarStore.getState().getMasterEvent({
+        id: 'ev1:a', originalId: 'ev1', recurrenceId: 'a', start: '2026-03-04T09:00:00',
+      } as any);
+
+      expect(mockGetEvents).toHaveBeenCalledWith(['ev1'], undefined);
+      expect(master?.id).toBe('ev1');
+      expect(master?.start).toBe('2026-03-02T09:00:00');
+    });
+
+    it('getMasterEvent returns a master as-is', async () => {
+      const ev = { id: 'ev1', recurrenceRules: [{ frequency: 'daily' }] } as any;
+      expect(await useCalendarStore.getState().getMasterEvent(ev)).toBe(ev);
+      expect(mockGetEvents).not.toHaveBeenCalled();
+    });
   });
 });
diff --git a/src/stores/calendar-store.ts b/src/stores/calendar-store.ts
index 06eaf28f..4f61dc0e 100644
--- a/src/stores/calendar-store.ts
+++ b/src/stores/calendar-store.ts
@@ -16,6 +16,7 @@ import {
 } from '../api/calendar';
 import { jmapClient } from '../api/jmap-client';
 import { expandRecurringEvents } from '../lib/recurrence-expansion';
+import { isRecurringSeriesMember } from '../lib/recurrence-overrides';
 
 // Does the event carry attendees the server should notify over iMIP? Used to
 // decide whether to set sendSchedulingMessages on create/update/delete.
@@ -84,8 +85,13 @@ export interface CalendarState {
   refresh: () => Promise<void>;
   handleStateChange: (change: StateChange) => Promise<void>;
   createEvent: (event: Partial<CalendarEvent>, calendarId: string) => Promise<CalendarEvent>;
-  updateEvent: (id: string, changes: Partial<CalendarEvent>) => Promise<void>;
+  // `changes` may be a plain partial or a JMAP patch with JSON-pointer keys
+  // (e.g. `recurrenceOverrides/<recurrenceId>`).
+  updateEvent: (id: string, changes: Partial<CalendarEvent> | Record<string, unknown>) => Promise<void>;
   deleteEvent: (id: string) => Promise<void>;
+  // Resolve a client-side expanded occurrence (or a master) to its master
+  // event, fetching it from the server when the expansion replaced it.
+  getMasterEvent: (event: CalendarEvent) => Promise<CalendarEvent | null>;
   // Invitations / scheduling
   rsvpEvent: (
     eventId: string,
@@ -307,14 +313,34 @@ export const useCalendarStore = create<CalendarState>()(
     // Resolve client-side expanded occurrence IDs back to the master event ID.
     const storeEvent = get().events.find((e) => e.id === id);
     const realId = storeEvent?.originalId || id;
+    // Remap namespaced (shared-calendar) store ids in calendarIds back to the
+    // raw server ids the owning account knows.
+    const patch: Record<string, unknown> = { ...changes };
+    const calendarIds = patch.calendarIds as Record<string, boolean> | undefined;
+    if (calendarIds && typeof calendarIds === 'object') {
+      const remapped: Record<string, boolean> = {};
+      for (const [calId, v] of Object.entries(calendarIds)) {
+        const cal = get().calendars.find((c) => c.id === calId);
+        remapped[cal?.originalId || calId] = v;
+      }
+      patch.calendarIds = remapped;
+    }
     // Notify attendees if either the stored event or the incoming changes
     // carry participants.
     const schedule =
-      hasSchedulingParticipants(changes) || hasSchedulingParticipants(storeEvent);
-    await apiUpdateEvent(realId, changes, schedule ? true : undefined, storeEvent?.accountId);
+      hasSchedulingParticipants(changes as Partial<CalendarEvent>) ||
+      hasSchedulingParticipants(storeEvent);
+    await apiUpdateEvent(realId, patch, schedule ? true : undefined, storeEvent?.accountId);
     set({
-      events: get().events.map((e) => (e.id === id ? { ...e, ...changes } : e)),
+      events: get().events.map((e) => (e.id === id ? { ...e, ...(changes as Partial<CalendarEvent>) } : e)),
     });
+    // A series mutation (an occurrence override, a truncated/changed rule, a
+    // master edit) touches every expanded sibling, and the optimistic merge
+    // above only updated the tapped one — reload the visible range like
+    // webmail's refetchAfterOccurrenceMutation.
+    if (storeEvent && isRecurringSeriesMember(storeEvent)) {
+      await get().refresh();
+    }
   },
 
   deleteEvent: async (id) => {
@@ -325,7 +351,27 @@ export const useCalendarStore = create<CalendarState>()(
       hasSchedulingParticipants(storeEvent) ? true : undefined,
       storeEvent?.accountId,
     );
-    set({ events: get().events.filter((e) => e.id !== id) });
+    // Destroying a master removes every expanded occurrence of it, not just
+    // the tapped one.
+    set({ events: get().events.filter((e) => e.id !== id && (e.originalId || e.id) !== realId) });
+    if (storeEvent && isRecurringSeriesMember(storeEvent)) {
+      await get().refresh();
+    }
+  },
+
+  getMasterEvent: async (event) => {
+    if (event.recurrenceRules?.length && !event.recurrenceId) return event;
+    // Client-side expansion replaces the master with its occurrences, each
+    // pointing back at the master's server id through originalId.
+    const realId = event.originalId || event.id;
+    const inStore = get().events.find(
+      (e) => e.id === realId && !e.recurrenceId && !!e.recurrenceRules?.length,
+    );
+    if (inStore) return inStore;
+    const fetched = (await fetchEvents([realId], event.accountId)) ?? [];
+    const master = fetched[0];
+    if (!master) return null;
+    return mapServerEventToStoreEvent(master, get().calendars, event.accountId);
   },
 
   rsvpEvent: async (eventId, participantId, status, replyTo) => {